1. Field of the Invention
The present invention relates to a process for manufacturing a cycloolefin addition polymer. More particularly, the present invention relates to a process for manufacturing a cycloolefin addition polymer having a narrow molecular weight distribution and a controlled molecular weight. The process can achieve a high polymerization conversion rate and is suitable for industrially manufacturing the cycloolefin addition polymer.
2. Description of Related Art
Polymers formed from a structural unit which mainly originates from cycloolefin compounds are manufactured by using a catalyst containing a metal compound component of a metal belonging to Group 10 such as nickel and palladium. These polymers are known as resins having outstanding heat resistance and transparency. It has been reported that a cycloolefin addition polymer exhibiting high polymerization activity and possessing outstanding transparency, heat resistance, and mechanical strength can be manufactured by using a specific catalyst containing in particular a palladium compound. See JP-A-2006-52347, JP-A-2005-162990 and JP-A-2005-213435.
JP-A-2005-48060 discloses a crosslinked product of cycloolefin addition copolymer containing a hydrolyzable silyl group-containing cycloolefin, which can be produced by using a catalyst containing a palladium compound, and possesses excellent heat resistance, mechanical strength, and dimensional stability. In order to exhibit such performance, the cycloolefin addition copolymer must have sufficiently reduced compositional distribution. To this end, a method of introducing a part of hydrolyzable silyl group-containing cycloolefin during the polymerization reaction and a continuous polymerization process have been proposed. However, the document discloses neither a method and effect of obtaining a polymer with a narrow molecular weight distribution, nor a method of easily controlling the polymerization temperature. In addition, the disclosed technology is applicable only to hydrolyzable silyl group-containing cycloolefin copolymers.
Since the molecular weight of a cycloolefin addition copolymer significantly affects the solubility in solvent, solution viscosity, melting behavior, mechanical strength, and the like, it is important to control the molecular weight in an optimal range according to the application and molding method. As a method for controlling the molecular weight, for example, a method of adding a 1-alkene and an aromatic vinyl compound as a molecular weight controlling agent has been disclosed, and a mechanism of inserting a double bond into a metal-carbon bond and beta-hydrogen dissociation which follows the double bond insertion has also been proposed. See JP-A-2005-162990, JP-T-9-508649 And JP-A-2003-40929. In contrast, no considerable attention has been given to the molecular weight distribution of a cycloolefin addition copolymer. Many manufacturing processes produce low molecular weight components. Since low molecular weight components included in a polymer may degrade mechanical strength and heat resistance, sufficient reduction of the low molecular weight components is often desired. As an example of related art giving attention to the molecular weight distribution, a method of manufacturing a norbornene-based cycloolefin addition polymer in which the molecular weight and the molecular weight distribution are controlled by the addition of a non-conjugated cyclopolyene has been disclosed, see JP-A-2002-212209. However, the non-conjugated cyclopolyene firmly coordinates with a transition metal compound, which may result in lowering polymerization activity.
On the other hand, the polymerization temperature largely affects the reaction rate, life of active seeds, and properties of polymers. For example, if the polymerization temperature is too high, the catalyst may be deactivated, resulting in an insufficient conversion rate. If the polymerization temperature is too low, the productivity may unduly decrease. In addition, a temperature variation may affect the molecular weight and the like. If the control range is too wide, uniformity of the polymer may be impaired. Since a decrease of the specific surface area of the reactor due to the increase in the reactor capacity gives rise to reduction of cooling efficiency of the polymerization system, effective removal of heat and control exothermic heat are important subjects in controlling the reaction temperature. In order to increase economy in industrial production and to maintain the product quality, a process for manufacturing cycloolefin addition copolymers with excellent temperature control has been desired.
However, a process for manufacturing a cycloolefin addition copolymer which can attain narrow molecular weight distribution, can allow easy control of the polymerization temperature, and is particularly suitable for industrial production has not been reported up to now.
The processes for manufacturing cycloolefin addition polymers presently used have a problem of producing a large amount of low molecular weight components, particularly when a high conversion rate is pursued.